Bluetooth: Truncate received OPP file name instead of rejecting it

Including extn of the file, Linux supports 255 character as a maximum
length of the file name to be created. Hence, Instead of sending
OBEX_HTTP_INTERNAL_ERROR as a response, truncate the length of the
file name and save it. This check majorly helps in the case of vcard,
where Phone book app supports contact name to be saved more than 255
characters, But the server rejects the card just because the length of
vcf file name received exceeds 255 Characters.

Change-Id: Icaceddbfd7b9431712f7b98b601016e753b1569c